Web breaking control in drying apparatus



April 16, 1963 E. J. JUSTUS WEB BREAKING CONTROL IN DRYING APPARATUS 4Sheetsheet 1 Filed March 9, 1960 'QY-Z A ril 16, 1963 E. J. JUSTUS WEBBREAKING CONTROL IN DRYING APPARATUS Filed March 9, 1960 4 Sheets-Sheet2 .[UFEHfUP a a7' .7. ustus April 16, 1963 E. J. JUSTUS WEB BREAKINGCONTROL IN DRYING APPARATUS 4 Sheets-Sheet 3 Filed March 9, 1960[HI/EHJUF [Li ya? Jus us April 16, 1963 E. J.- JUSTUS WEB BREAKINGCONTROL IN DRYING APPARATUS 4 Sheets-Sheet 4 Filed March 9, 1960 R &

[HI/E11 0!" Q fd 'arffustus Hff 5 3,085,347 WEE BREAKING CONTROL INDRYING APPARATUS Edgar J. Justus, Beloit, Wis, assignor to Beloit IronWorks, Beloit, Wis, a corporation of Wisconsin Filed Mar. 9, 1960, fier.No. 13,991 it) (Ilaims. (Cl. 34-49) The present invention relatesbroadly to drying apparatus, and is more particularly concerned with ahigh velocity air dryer of the recirculating type especially suitable inthe paper making art and featuring therein the provision of paper webbreak detection means effective to initiate a plurality of steps inwhich exhaust air flow is reversed to render essentially remote systemcontamination from broken web pieces and the ignition of said particleswithin the system.

Relatively recently high velocity air drying has been practiced toaugment the drying effect of conventional cylinder dryers and therebyattain higher production rates in paper making machines. Current demandsfor coating of papers on the paper machine have required added dryingcapacity, as is well known, often where space is limited. One dryingsystem having a high order of proven effectiveness is of therecirculating air type embodying air delivery duct means mounting asuitable nozzle pattern and exhaust duct means communicating with a hoodbeneath which the web passes during performance of the drying step. Itis not infrequent that the web will break in the region of the hood, andthe bits and pieces of web are then carried by the exhaust duct meansinto the blowers, into the heating means, and by the air delivery ductmeans, into the nozzle structure. Some of the broken web particles mayremain in the ducting, and with respect to the nozzle structure, anybits and pieces of web therein can at least interfere with theuniformity of air flow to a degree sufiicient to cause uneven drying,and can under more severe conditions jam the nozzle structure and eventhe ducting. As well, the presence of relative fine web particles withinthe hood and adjacent thereto with continued hot air input creates avery serious fire hazard, endangering operating personnel.

It is an important aim of the present invention to provide improveddrying apparatus which reduces to a minimum fire hazards and effectivelysolves other problems arising upon occasion of a web break.

Another object of this invention lies in the provision of arecirculating high velocity air dryer system, embodying therein means incontrol of an exhaust fan, air heating means, exhaust air flow path,fresh air supply, and hood position with respect to the web being dried.

Still another object of this invention is to provide a high velocity airdryer having air delivery duct means and exhaust duct means inassociation with means providing a unidirectional ilow path ofessentially unheated air through the air delivery and exhaust duct meansin response to a web break signal. 7

-A further object of the instant invention lies in the prosivision ofapparatus for drying paper webs and the like, embodying a hood, ductmeans delivering air to the hood and exhausting air therefrom, meansconnecting the air delivery and exhaust duct means, means closing theconnecting means during normal operation of the drying apparatus, blowermeans connected to the air delivery and exhaust duct means directing airto the hood through the air delivery duct means and receiving air fromthe hood through the exhaust duct means during normal operation of thedrying apparatus, closure means in the exhaust duct means between theconnecting means and the blower means open during normal operation ofthe drying apparatus and closed when a web break occurs to block returnof air from the hood to the blower means, and

sheet break detection means connected to the means closing theconnecting means and to the closure means to close the closure means andopen the means closing the connecting means and provide a unidirectionalair flow path from the blower means through the air delivery and exhaustduct means to the hood when a web break occurs.

Other objects and advantages of the invention will become more apparentduring the course of the following description, particularly when takenin connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughoutthe same:

FIGURE 1 is a more or less diagrammatic view of a dryer section of apaper machine illustrative of an exemplary environment for the presentinvention;

FIGURE is a vertical sectional view, with parts thereof in elevation, ofone form of dryer hood means and duct means which can be employed in thepresent invention;

FIGURES 3 and 4 are fragmentary plan views of air delivery nozzle meanssuitable for use with this invention;

FIGURE 5 is an end elevational view of a high velocity air dryerembodying the novel concepts-of this invention;

FIGURE 6 is a side elevational view of the structure of FIGURE 5; and

FIGURE 7 is a more or less diagrammatic view of the drying apparatus ofthis invention with a circuit diagram indicated thereon to more clearlyilustrate the steps of the instant invention upon occurrence of a webbreak.

Referring now to FIGURE 1, there is shown somewhat diagrammatically adry end section 10 of drying apparatus of a paper machine with which theinstant invention may be employed. However, it will be readily apparentduring the course of the description now to follow that the drying meansand method herein disclosed is also effective when installed subsequentto paper coating apparatus and that this invention is not restricted touse on a paper machine dryer. The techniques herein disclosed are ofequal application in textile drying and in the drying of particulate andsheet materials wherein it is important to rapidly obtain a reverse airflow and to terminate certain other functions in the normal dryingcycle.

The dry end section 10 shown in FIGURE 1 comprises a first row ofhorizontally aligned drying cylinders or drums lla-d of which four areshown in the exemplary embodiment illustrated, and a second row ofhorizontally aligned drying cylinders 12ad staggered with respect to thedrying drums 11 of the first row. A Web of paper W passes alternatelyabout the drying cylinders 11 and 12, and is maintained in contact withthe surfaces of the drying cylinders 11a and 11b by a felt 13, andagainst the surfaces of the drying drums 1241-41 by a felt 14. Asuitable number of rollers 15 are arranged to guide the felt 13, androllers 16 guide the felt 14. The drying arrangement as thus fardescribed Will be recognized as of an essentially conventionalconstruction, and the general-practice in the art is to Wrap the web Wabout drying cylinders 11 and 12. However, cylinders are not at alltimes required, and the instant invention can be practiced utilizing ahood positioned with its mouth portion relatively closely adjacent apaper web advanced along a generally straight line, rather thanserpentine, path.

Drying apparatus generally designated by the legend A and as constructedin accordance with the principles of this invention comprises a housingor insulated hood cover 18 having a length preferably coextensive withthe width of the web W and provided with a bottom opening 19 therein, sothat When the housing is suitably supported it overhangs the cylinder11c approximately to the distance shown. Stated otherwise, the housingor hood 18 extends a sufficient distance about the cylinder or drum 11cto be coextensive with the wrap of the web W during travel along thecircumferential portion of the rotatable drum 110.

The housing 18 may be shaped to provide a pair of generally uprightopposed sidewalls 20 and 21, a pair of opposed endwalls 22 and 23', agenerally flat top wall 24, and a generally arcuately curved bottom wall25 providing a confined path of web travel for the web during itswrapping contact with the drum 11c.

In the exemplary form of housing 18 shown in the drawings, there issupported interiorly thereof a plurality of circumferentially spacedsupply or air delivery plenums Zea-d, four of which are illustrated,although of course the number may vary. Each supply plenum 26 may be ofgenerally semi-cylindrical shape, and the plenum means 26ad communicate,respectively, with conduit means 27ad leading to a header 28 whichconnects with branch portion 29a of air delivery duct means 29. Toexhaust moisture bearing air from the housing 18, and to provide areverse air flow or air delivery to the housing 18 when a sheet breakoccurs, the housing top wall 24 receives branch portions 30a and 31a ofexhaust du-ct means 30 and 31.

As will be described hereinafter, the air delivery branch portion 29aand exhaust branch portions 30a and 31a may have slidable connectionwith other portions of the air delivery and exhaust duct means 2931 topermit the hood 18 to be raised along said branch portion 29a, 30a and31a when a sheet break occurs.

Each supply plenum 26 supports nozzle means 32a-d, which may take anumber of diiferent forms having various air delivery patterns thereinwhich, if desired, may be arranged as in FIGURES 3 and 4. The nozzlemeans 32 may have a plurality or array of spaced holes or perforations33 (FIGURE 3) of a particular configuration, diameter and number inorder to obtain maximum drying efficiency, or, the nozzle means 32 inthe form of a plate may have spaced slots 34 (FIGURE 4) which may bestraight walled or tapered and of a spacing, width and number to obtainthe desired drying efiiciency. It may be noted from FIGURE 2 that theperforated or slotted plates 32 close the mouth portion of each supplyplenum 26, and to assure that the air stream issuing therefrom impingeagainst the paper web W generally normal thereto, each plate 32 is ofgenerally arcuate shape when viewed in end, or as may be otherwisestated, each plate or nozzle member 32 has a curvature corresponding tothat of the cylinder or drum 11c.

As is best shown in FIGURES and 6, the air delivery branch portion 29aof the duct means 29 is telescopingly received in a branch portion 2%,while the exhaust duct branch portions 30a and 31a may telescope Withinbranch portions 305 and 31b of the exhaust duct means 30 and 31. Furtherdetails of the means to raise and lower the hood 18 will be laterdescribed, although it may now be noted that the hood end walls 22 and23'may mount brackets 35 to which are connected pistons 36 of pneumaticor hydraulic cylinders 37 secured in any suitable manner to a fixedstructure, as indicated in FIGURES 5 and 6.

The air delivery duct branch portion 29b is generally verticallydisposed and integral therewith or in some other suitably connected in agenerally horizontal duct branch portion or run 29c leading to agenerally upright or vertically disposed duct branch portion 290!terminating in a blower housing 38. The exhaust d-uct branch portions361) and 3117, on the other hand, may be connected to inclined branchportions 300 and 31c connected to curved or elbow branch portions 30dand 31d which merge or combine into a common horizontal branch portionor run designated generally as 3012. The horizontal run or branchportion 36c leads to a generally upright branch portion 30 connected tothe blower housing 38, and upstream therefrom is a reduced diameterbranch portion 30g leading to an exhaust fan housing 39.

The drying apparatus A as thus far described is supported in anysuitable manner by a fixed structure. The support means for the airdelivery and exhaust ducting may include longitudinally extending beams40 (FIGURE 5), while the blower housing may be mounted upon stand means41 and the exhaust fan housing 39 upon stand means 42 erected from awall portion 43. The blower housing 38 mounts interiorly thereof fanmeans 44 indicated diagrammatically as driven through belt means 45 frommotor means 46. A similar arrangement is provided for the exhaust fan,and motor means 47 supported upon the wall portion 43 is connected bybelt means 48 to fan means 49 within the exhaust fan housing 39. Freshor makeup air is supplied to the system through duct means 50communicating with the blower housing 38, and within the duct means 50is a damper or bfle member 51 to control the amount of air admitted tothe housing 38. In the system illustrated, the damper means 51 isnormally in a partially open position, and when a sheet break occurs aswill later be described in detail, the damper means 51 is fully opened.Of course, between the damper means 51 and the blower housing 38, apermanently open inlet vane structure could be provided.

T he exhaust fan housing 39 also mounts duct means 52 having dampermeans 53 therewithin which is normally in a partially open position tovent from the system moisture laden air drawn by the fan means 49through the exhaust duct means 30 and 31. When a sheet break occurs,however, the damper means 53 is caused to move to a fully open positionunder control of the air flow control system herein provided, to permitthe input of a maximum amount of fresh air to the system for portingthrough the air delivery duct means 2-9 and exhaust duct means 30 and31.

Additional damper means are herein provided for actuation when a sheetbreak occurs to block return air fiow to the blower 44 and to provide aunidirectional air flow from the blower means 44 through the airdelivery and exhaust duct means 29-31, A first such damper means isherein referred to as an isolation damper, and is designated in FIGURES5 and 7 by the numeral 54. The isolation damper 54 is located in thecommon horizontal run We leading from the exhaust duct portions 39d and31d to the vertical duct portion 30 which terminates in the blowerhousing 38. It may now be seen that when the isolation damper 54 isactuated to a closed portion, normal flow of moisture laden air from theexhaust duct means 30 and 31 to the blower housing 38 is blocked, sothat hits and pieces of broken web are not permitted to contaminate theblower means 44 and exhaust fan means 49, nor the ducting leading to theblower and exhaust fans. The manner in which the isolation damper 54 isactuated will be later described in connection with FIG- URE 7.

A further damper means provided in accordance with this invention isherein termed a by-pass or blow-back damper, and is designated inFIGURES 5, 6 and 7 by the numeral 55. The damper 55 is positioned in aconnecting duct 56 extending between the air delivery duct portion 290and the common exhaust duct horizontal portion 302 The by-pass damper 55is normally closed, however, when a sheet break occurs, the bypassdamper 55 is automatically actuated to an open position to provide anair flow path from the blower housing 38 through the air deliveryvertical duct portion 29d and through the air delivery horizontal run29c through the auxiliary duct means 56 and through the air delivery andexhaust duct portions 30d, 31d, 29b-31b and 29a-31a to the interior ofthe hood 18. The damper actuating means and the automatic systemprovided therefor will be noted in detail in connection with FIGURE 7.

During normal operation of the drying apparatus A,

air directed through the air delivery duct means 29 is increased intemperature to a level sufficient for effective drying of the travelingpaper web W. For this purpose, heating means 57 are supported'in thegenerally vertical duct portion 29d of the air delivery duct 25?,although of course this position can well be varied. The heating means57 may take various forms, as for example, steam coils or combustion airheaters. The heating means 57 are indicated somewhat diagrammatically inFIGURE 7 as electrical heating means, although generally speakingresistanoe heaters may not be desired because of the fire hazardsinvolved.

Referring again to FIGURE 7, there is shown a rapid acting, highlyreliable and relatively simple air flow control system operable uponoccurrence of a web break to stop operation of the exhaust fan 49, shutoil the heating means 57, close the exhaust air flow path to the exhaustfan 49 and blower means 44 through closing of the isolation damper 54,provide a unidirectional air flow path from the blower 44 through theair delivery duct means 29 and exhaust air duct means 36 and 31 byopening of the bypass damper 55, and to raise the hood 18 by actuationof the cylinders 37. Other functions are performed when a sheet breakoccurs, and these will now be noted in the succeeding paragraphs.

In accordance with the principles of this invention, the occurrence of aweb break is detected by a photoelectric cell or like device 60 (FIGURE7) preferably positioned relatively close to the drying cylinder 11c,and if desired mounted by the hood means 18 adjacent the mouth 19thereof. The break detector 65 is electrically connected to a controlcircuit 61 operating on 115 volts and 60 cycle current from leads L-1and L-Z. The control circuit 61 operates a relay 62 in control of a pairof normally open switches 63 and 64 and a normally closed switch 65. Theswitch 65 when closed completes a circuit to a relay 66 in control ofthe exhaust fan motor 47, which in turn is supplied with power throughleads L-3, L-4 and N. As is indicated in FIGURE 7, the blower fan motor46 operates continuously in the event of a web break, and its operationis terminated only under control of a master switch 67.

With the exception of the blower fan and exhaust fan motors 46 and 47,the various earlier named functions of shutting oil the flow of heatingfluid to the heating means 57, operating the dampers and raising thehood 18 are performed by a pneumatic system, although it will be readilyapparent that a hydraulic system could as well be employed. Thepneumatic system under control of the illustrated circuitry includes amain compressed air line 68 serving valve means 69, 7t) and 71, which inturn are respectively controlled by solenoids 72, 73 and 74. Thesolenoid 72 is electrically connected to the control circuit 61 and tothe normally open switch 63, while the normally open switch 64 leads tothe solenoids 73 and 74. The valve means 69 served by the compressed airline 68 controls the flow of fluid through lines 75 and 76 leading tothe pneumatic motors 37 and thereby control raising or lowering of thehood 1%. The pneumatic motors 37 are shown somewhat diagrammatically inFIGURE 7, four pneumatic motors 37 being provided for effective raisingand lowering the hood.

Compressed air from the main line 68 leads by branch line 77 to thevalve means 70 and 71. The valve means '70 is first. in control of airmotors 78 and 79 connected to the bypass damper 5'5 and isolation damper54, respectively. The valve 70 further controls fluid flow through abranch line 80 leading to an air motor 81 for the exhaust fan damper 53,and through a branch connection 82 to an air motor 83 for the makeup airdamper 51. The valve means 71, on the other hand, upon actuation by thesolenoid 74 controls an air motor 84 to terminate steam how to theheater means 57.

The operation of the instant control system may be described as follows.When a sheet break occurs, the absence of the web sends a signal to thecontrol circuit 61, operating the relay 62 and generally simultaneouslythe solenoid 72 in control of the valve means 69. Actuation of the relay62 opens the switch means 65 which operates the relay 66 in control ofthe exhaust fan motor 47 .to shut off said motor. Actuation of the relay62 further closes the switch means 64 to operate the solenoid 74, whichis in control of the valve means 71, causing compressed air flow to theair motor 84 to shut olf steam flow to the heater means 57. The switchmeans 64 upon movement from a normally open to a closed positionactuates the solenoid 73 and in turn the valve means 70 to close theisolation damper 54 and open the bypass damper by means of the airmotors 79 and 78, respectively. Opening of the valve means 7% furtherprovides a compressed air flow path through the conduit 80 to the airmotor 81 to open the exhaust fan damper 53, and through the conduit 82,to open the makeup air damper 51. By action of the relay 62, thenormally open switch 63 is closed, to complete a circuit to the solenoid72, opening the valve means 69 and permitting compressed air flow to thepneumatic motors 37 to raise the hood 18 upwardly from the dryingcylinder 11c.

Closing of the isolation damper 54 blocks the exhaust air duct means 30and 31 downstream of the by-pass connection 56, so that any bits andpieces of broken paper web cannot be drawn down the exhaust ductportions 30:: and 30 to the blower 44. This prevents contamination ofthe blower 44 and clogging or other contamination of the exhaust airduct means 30 and 31 and the air delivery duct means 29. The exhaust airdamper 53 and the makeup air damper 51 are in a fully open position, asdescribed, and accordingly the blower mo tor 44 draws through theducting 52 and 50 a relatively large supply of fresh air for directionthrough the air delivery duct portion 29d to the bypass connection 56,and from said connection past the open by-pass damper and through theduct portions 29b-31b and 29a31a through the nozzle means 32 and aroundthe plenums 26a-d and outwardly through the hood means mouth portion 19.

It is of course appreciated that the air heated by the heater means 57is at a relatively high temperature for efiective web drying, and thateven when the heat supply to the heater means 57 is terminated, asubstantial amount of residual heat remains in the air and that thereremains a possibility of ignition of the relatively fine web particleswithin the hood 18. However, by this invention, since substantialvolumes of ambient air are directed into the hood 18 from the blower 44,and since the hood 18 is raised away from the drying cylinder 110, thereis essentially no likelihood of overdrying of the web particles suchthat ignition of the particles could take place.

Raising of the hood means 18 by the pneumatic motors 37 upon detectionof a web break also permits ready rethreading of the web W about thedrying cylinder 11c, and when the web W is properly in location, thephotoelectric cell 60 through the control circuit 6-1 (assuming the mainswitch 67 is closed) closes the switch 65 and opens the switches 63 and64 under action of the relay 62. Generally the reverse sequence of stepstakes place, as compared with the steps described in connection with aweb break'condition, and the exhaust fan motor is again started, heatsupplied to the heater means 57, the isolation damper 54 opened and theby-pass damper 55 closed. The exhaust fan damper is closed, the makeupair damper 51 placed in a partially closed position, and the hood 18lowered by the pneumatic motors 37. The normal air flow path is therebyrestored, and in this cycle a portion of the moisture laden air iswithdrawn from the system through the exhaust air duct portion 30g underaction of the exhaust fan motor 49. The remaining portion of themoisture laden air is circulated by the blower 44- across the heatingmeans 57 and through the air delivery duct 29 from which it issuesthorugh the nozzle slots or openings in the nozzle plates 32. The heatedair issuing through the openings 33 or slots 34 impinges generallynormally against the paper web W, and under action of the exhaust fan49, the air is withdrawn from adjacent the nozzle plates 32 in generallythe directions indicated by the arrows in FIGURE 2. This air is thenwithdrawn from the hood interior through the exhaust air duct means 30and 31, to be recirculated through the system as described. Air issuingfrom the slots or openings in the nozzle plates 32 is at substantialvelocities of the order of from 15,000 to 30,000 feet per minute, and itis believed readily apparent that any control system to effect a reverseair flow of the exhaust air must have quick response or be rapid acting.Of course, the air delivered through the air delivery duct 20 andthrough the nozzle plates 32 is at a first or relatively high pressure,greater than the air pressure within the hood 18 and greater than thepressure of the air being exhausted through the duct means 30 and 31.The pressure within the hood 18 is of course greater than the airpressure in the exhaust duct means 30 and 31, and when a web breakoccurs and the isolation damper 54 is closed, the air following aunidirectional flow path through the duct means 29, 30 and 31 is at afourth pressure between the orignal air delivery pressure and theexhaust air pressure. Thus, as compared with normal operation of thedrying apparatus A, when a sheet break occurs pressure in the airdelivery duct 29 decreases and the pressure in the exhaust air ductmeans 30 and 31 increases.

The instant control system effectively prevents combustion of readilyignitable fibrous particles upon occasion of a web break, and furtherprevents clogging of the nozzle means and ducting so that at all times auniform air flow and uniform web drying are provided. It has been notedhereinabove that the dampers and hood could be hydraulically actuated inresponse to a web break signal, and of course other variations andmodifications can be effected without departing from the novel conceptsof this invention. 7

I claim as my invention:

1. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said Web, duct means delivering air to thehood, duct means exhausting air from said hood, means connecting the airdelivery and exhaust duct means, means closing the connecting meansduring normal operation of the drying apparatus, blower means connectedto the air delivery and exhaust duct means directing air to the hoodthrough the air delivery duct means and receiving air from the hoodthrough the exhaust duct means during normal operation of the dryingapparatus, damper means in the exhaust duct means between the connectingmeans and the blower means open during normal operation of the dryingapparatus and closed when a web break occurs to block return of air fromthe hood to the blower means, means mounted to detect a break in saidweb, and control means responsive to said Web break detection means andconnected to the means closing the connecting means and to the dampermeans to close the damper means and open the means closing theconnecting means and provide a unidirectional air flow path from theblower means through the air delivery and exhaust duct means to the hoodwhen a web break occurs.

2. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, means for raising and lowering thehood, duct means delivering air to the hood, duct means exhausting airfrom said hood, means connecting the air delivery and exhaust ductmeans, means closing the connecting means during normal operation of thedrying apparatus, blower means connected to the air delivery and exhaustduct means directing air to the hood through the air delivery duct meansand receiving air from the hood through the exhaust duct means duringnormal operation of the drying apparatus, damper means in the exhaustduct means between the connecting means and the blower means open duringnormal operation of the drying apparatus and closed when a web breakoccurs to block return of air from the hood to the blower means, meansmounted to detect a break in said web, and control means responsive tosaid web break detection means and connected to the means closing theconnecting means, to the damper means and to the means for raising andlowering the hood to close the damper means and open the means closingthe connecting means and provide a unidirectional air flow path from theblower means through the air delivery and exhaust duct means to the hoodwhen a web break occurs while raising the hood to permit ready access tothe web.

3. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, a blower for supplying air to saidhood, air delivery duct means connecting the hood and blower, exhaustair duct means connecting the blower and hood, junction conduit meansbetween the air delivery and exhaust air duct means, closure means insaid conduit means closed during normal operation of the dryingapparatus, damper means in the exhaust air duct means open during normaldryer operation and closed when a web break occurs to provide with theconduit means and closure means therein an air flow path of Yconfiguration from the blower through the conduit means to the hood,means responsive to a sheet break signal, and control means connected tosaid last-named means to open the closure means and close the dampermeans to provide the named flow path from the blower to the hood.

4. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, duct means delivering air to thehood, duct means exhausting air from said hood, means connecting the airdelivery and exhaust duct means, damper means closing the connectingmeans during normal operation of the drying apparatus, blower meansconnected to the air delivery and exhaust duct means directing air tothe hood through the air delivery duct means and receiving air from thehood through the exhaust duct means during normal operation of thedrying apparatus, closure means in the exhaust duct means between theconnecting means and the blower means open during normal operation ofthe drying apparatus and closed when a web break occurs to block returnof air from the hood to the blower means, heater means in the airdelivery duct means, motor means connected to the damper means and tothe closure means, means mounted to detect a break in said web, andcontrol means responsive to said web break detection means and connectedto the heater means and motor means for the damper and closure meanseffective when a web break occurs to shut off heating fluid to theheating means and to close the closure means while opening the dampermeans to provide a unidirectional air flow path from the blower meansthrough the air delivery and exhaust duct means to the hood when a webbreak occurs.

5. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, duct means delivering air to thehood, duct means delivery and exhaust duct means directing air to thehood through the air delivery duct means and receiving air from the hoodthrough the exhaust duct means during normal operation of the dryingapparatus, closure means in the exhaust duct means between theconnecting means and the blower means open during normal operation ofthe drying apparatus and closed when a web break occurs to block returnof air from the hood to the blower means, an exhaust fan connected tothe exhaust air duct to withdraw air from the hood during normaloperation of the drying apparatus, means for raising and lowering thehood, heater means in the air delivery duct means, motor means connectedto the damper means and to the closure means, means mounted to detect abreak in said web, and control means responsive to said web breakdetection means and connected to the heater means, exhaust fan, meansfor raising and lowering the hood, and motor means for the damper andclosure means effective when a web break occurs to shut ofi heatingfluid to the heating means, stop the exhaust fan, raise the hood and toclose the closure means while opening the damper means to provide aunidirectional air flow path from the blower means through the airdelivery and exhaust duct means to the hood when a web break occurs.

6. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, duct means delivering air to thehood, duct means exhausting air from said hood, means connecting the airdelivery and exhaust duct means, damper means closing the connectingmeans during normal operation of the drying apparatus, blower meansconnected to the air delivery and exhaust duct means directing air tothe hood through the air delivery duct means and receiving air from thehood through the exhaust duct means during normal operation of thedrying apparatus, closure means in the exhaust duct means between theconnecting means and the blower means open during normal operation ofthe drying apparatus and closed when a web break occurs to block returnof air from the hood to the blower means, motor means connected to thedamper means and to the closure means, conduit means connected to asource of pressurized fluid and to the motor means for the closure anddamper means, valve means in said conduit means, solenoid meansconnected to said valve means, means mounted to detect a break in saidweb, and control means responsive to said web break detection means andelectrically connected to the solenoid means to actuate the valve meansand port pressurized air to the motor means, closing the closure meansand opening the damper means to provide a unidirectional air flow pathfrom the blower means through the air delivery and exhaust duct means tothe hood when a web break occurs.

7. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, duct means delivering air to thehood, duct means exhausting air from said hood, means connecting the airdelivery and exhaust duct means, damper means closing the connectingmeans during normal operation of the drying apparatus, blower meansconnected to the air delivery and exhaust duct means directing air tothe hood through the air delivery duct means and receiving air from thehood through the exhaust duct means during normal operation of thedrying apparatus, closure means in the exhaust duct means between theconnecting means and the blower means open during normal operation ofthe drying apparatus and closed when a web break occurs to block returnof air from the hood to the blower means, motor means connected to thedamper means and to the closure means, an exhaust fan connected to theexhaust air duct to withdraw air from the hood during normal operationof the drying apparatus, pneumatic means for raising and lowering thehood, conduit means connected to a source of pressurized fluid and tothe motor means for the closure and damper means and to the pneumaticmeans for the hood, valve means in said conduit means, solenoid meansconnected to said valve means, means mounted to detect a break in saidweb, and control means responsive to said web break detection means andelectrically connected to the exhaust fan and to the solenoid means toterminate operation of said fan and to actuate the valve means forporting pressurized air to the motor means and to the pneumatic meansfor the hood, closing the closure means and opening the damper means toprovide a unidirectional air flow path from the blower means through theair delivery and exhaust duct means to the hood when a web break occurswhile raising the hood to permit ready access to the Web.

8. Apparatus for drying paper webs and the like, comprising meansproviding a well supporting surface, a hood supported adjacent saidsurface during drying of said web, duct means delivering air to thehood, duct means exhausting air from said hood, flow control means inthe air delivery and exhaust air duct means controlling the admission ofair to the air delivery duct and the flow of moisture bearing air fromthe exhaust air duct, means connecting the air delivery and exhaust ductmeans, damper means closing the connecting means during normal operationof the drying apparatus, blower means connected to the air delivery andexhaust duct means directing air to the hood through the air deliveryduct means and receiving air from the hood through the eX- haust ductmeans during normal operation of the drying apparatus, closure means inthe exhaust duct means between the connecting means and the blower meansopen during normal operation of the drying apparatus and closed when aweb break occurs to block return of air from the hood to the blowermeans, heater means in the air delivery duct means, motor meansconnected to the damper means and to the closure means, an exhaust fanconnected to the exhaust air duct to withdraw air from the hood duringnormal operation of the drying apparatus, pneumatic means for raisingand lowering the hood, motor means connected to the flow control meansin the air delivery and exhaust air ducts, first conduit means connectedto a source of pressurized fluid and to the motor means for the closureand damper means, second conduit means connected to said source and tothe pneumatic means for the hood, and third conduit means also connectedto said source and to the motor means for the flow control means, valvemeans in each of said first, second and third conduit means, solenoidmeans connected to each of said valve means, means mounted to detect abreak in said web, and control means responsive to said web breakdetection means and electrically connected to the exhaust fan and to thesolenoid means, whereby upon a web break the exhaust fan is stopped, andpressurized air is admitted to the motor means for the damper andclosure means to close said closure means and open said damper means,providing a unidirectional air flow path from the blower means throughthe air delivery and exhaust duct means to the hood when a web breakoccurs, the pressurized air also opening the flow control means in theair delivery and exhaust air ducts, shutting off the supply of heatingfluid of the heating means and raising the hood upon occasion of a webbreak to permit ready access to the web.

9. In an apparatus for drying a fibrous web, a rotatable drum providinga Web supporting surface, a hood extending about a portion of thecircumference of said drum, means for raising and lowering said hood, anair delivery duct delivering air to said hood and the fibrous webpassing about said drum, an air exhaust duct for withdrawing spent airfrom said hood and fibrous web, air moving means directing air throughthe air delivery duct to said hood and for withdrawing spent air fromsaid hood through said exhaust duct, control means effective to directthe flow of air delivered by the air moving means through the airdelivery and exhaust ducts out It 1 through the hood including dampermeans in said exhaust duct andby-passing damper means for directing airfrom said delivery duct to said exhaust duct, web break detecting meansfor detecting a break in the Web passing about said drum, and meansoperative under the control of said web break detecting means forraising said hood and operating said control means to operate both ofsaid damper means to effect the delivery of air to said delivery andexhaust ducts out through the raised hood upon the detection of a breakin the Web.

10. Apparatus for drying paper webs and the like, comprising meansproviding a web supporting surface, a hood supported adjacent saidsurface during drying of said web, means for raising and lowering saidhood, a delivery duct for delivering air to the hood and Web, an exhaustduct for exhausting air from the hood, a con necting duct connectedbetween said ducts, damper means in said connecting duct closed duringnormal operation of the drying apparatus, air moving means directing airthrough the air delivery duct and exhausting air through the exhaustduct, normally open damper means in said exhaust duct, and control meanseffective when a Web break occurs, to raise the hood, open said dampermeans in said connecting duct and close said damper means in saidexhaust duct, to thereby provide a unidirectional air flow through theair delivery and exhaust ducts and out through the raised hood.

References Cited in the file of this patent UNITED STATES PATENTS2,166,379 Skagerberg July 18, 1939 2,268,988 Hess et al. Ian. 6, 19422,928,185 Drew Mar. 15, 1960 2,939,222 Svavar et a1. June 7, 1960FOREIGN PATENTS 748,080 Great Britain Apr. 18, 1956 770,240

Great Britain Mar. 20, 1957

1. APPARATUS FOR DRYING PAPER WEBS AND THE LIKE, COMPRISING MEANSPROVIDING A WEB SUPPORTING SURFACE, A HOOD SUPPORTED ADJACENT SAIDSURFACE DURING DRYING OF SAID WEB, DUCT MEANS DELIVERING AIR TO THEHOOD, DUCT MEANS EXHAUSTING AIR FROM SAID HOOD, MEANS CONNECTING THE AIRDELIVERY AND EXHAUST DUCT MEANS, MEANS CLOSING THE CONNECTING MEANSDURING NORMAL OPERATION OF THE DRYING APPARATUS, BLOWER MEANS CONNECTEDTO THE AIR DELIVERY AND EXHAUST DUCT MEANS DIRECTING AIR TO THE HOODTHROUGH THE AIR DELIVERY DUCT MEANS AND RECEIVING AIR FROM THE HOODTHROUGH THE EXHAUST DUCT MEANS DURING NORMAL OPERATION OF THE DRYINGAPPARATUS, DAMPER MEANS IN THE EXHAUST DUCT MEANS BETWEEN THE CONNECTINGMEANS AND THE BLOWER MEANS OPEN DURING NORMAL OPERATION OF THE DRYINGAPPARATUS AND CLOSED WHEN A WEB BREAK OCCURS TO BLOCK RETURN OF AIR FROMTHE HOOD TO THE BLOWER MEANS, MEANS MOUNTED TO DETECT A BREAK IN SAIDWEB, AND CONTROL MEANS RESPONSIVE TO SAID WEB BREAK DETECTION MEANS ANDCONNECTED TO THE MEANS CLOSING THE CONNECTING MEANS AND TO THE DAMPERMEANS TO CLOSE THE DAMPER MEANS AND OPEN THE MEANS CLOSING THECONNECTING MEANS AND PROVIDE A UNIDIRECTIONAL AIR FLOW PATH FROM THEBLOWER MEANS THROUGH THE AIR DELIVERY AND EXHAUST DUCT MEANS TO THE HOODWHEN A WEB BREAK OCCURS.